Ppm index

A Process Performance Index . A measure similar to the Ppk index that also takes into account variation between the process average and a target value. If the process average and the target are the same value, Ppm will be the same as Ppk. If the average drifts from the target value, Ppm will be less than Ppk.

where Pp is the classic performance index, T is the process target, x-doublebar is the Grand Average and σx is Sample Sigma .

Learn more about the SPC principles and tools for process improvement in Statistical Process Control Demystified (2011, McGraw-Hill) by Paul Keller, in his online SPC Concepts short course (only $39), or his online SPC certification course ($350) or online Green Belt certification course ($499).